Incidence and prevalence of psoriatic arthritis in patients with psoriasis stratified by psoriasis disease severity: Retrospective analysis of an electronic health records database in the United States.

BACKGROUND: Among patients in the United States with psoriasis (PsO), limited data exist on the incidence and prevalence of psoriatic arthritis (PsA) based on disease severity. OBJECTIVE: To assess the incidence, prevalence, and predictors of PsA among patients with PsO stratified by PsO severity using treatment type. METHODS: Incidence of PsA per 100 PsO patient-years (PY) and prevalence were assessed using the Optum electronic health records database. Incidence was assessed from PsO diagnosis and 1 year after PsO diagnosis overall and stratified by mutually exclusive treatment classes as a severity surrogate. RESULTS: The overall incidence of PsA was 2.9 (95% CI, 2.9-3.0) events per 100 PY. The incidence (95% CI) by severity surrogate was 2.1 (2.1-2.1), 9.9 (9.5-10.4), and 17.6 (16.9-18.3) events per 100 PY for patients with mild, moderate, and severe PsO as determined by receiving nonsystemics, nonbiologic systemic therapy, and biologics, respectively. When excluding patients diagnosed with PsA 1 year after PsO diagnosis, overall incidence was lower (1.7 [95% CI, 1.6-1.7] events per 100 PY), with similar trends for treatment-severity surrogates. LIMITATIONS: Results may not be generalizable to a wider population. CONCLUSION: The risk of developing PsA increased with disease severity and was highest in patients with the most severe PsO.